blacktop or concrete?

I am planning to build a building for storage of lawn care equipment,trailer,couple of quads and dirt bikes and to use as my workshop.It will be approx. 35'X45'with regular 2X4 wall construction,finished with siding.I had looked at concrete,but was told blacktop was much cheaper.Will blacktop be able to support this structure.Are concrete pilings still needed?how thick should the asphalt be laid?Thanks for any help.

It sounds like your gonna build your walls on top of the asphalt. Why not look into a perka building www.perka.com This building you can use sonno tubes to suport your frames and al your perlins and side wall support are wood.then pour a concrete floor.Asphalt wood be cheaper than concrete for your floor but conrete would be better support and if you put plastic under it it will keep moisture from comming up from the ground.

DO NOT build this building on an asphalt foundation. Asphalt is not suitable as a foundation for a structure. You could construct a pier foundation as cat320 mentioned, or build a grade beam of concrete around the perimiter to set the walls on. Asphalt is not rigid and will "creep" and flex over time.
Don't try to save money on a foundation. It will cause you problems that will be expensive to fix later on.

These guys are right nothing can beat the strength of concrete and the only thing approved by the building dept if your going todo this the legal way. The problem with blacktop is it does move and shift you will have sinking all over and if you got machines that are drippers you will end up with soft spots.